Chapter 1: Scientific Thinking

1. Chapter 1: Scientific Thinking Your best pathway to understanding the world Lectures by Mark Manteuffel, St. Louis Community College

3. Scientists • Are curious • Ask questions about how the world works • Seek answers • Does the radiation released by cell phones cause brain tumors? • Are anti-bacterial hand soaps better than regular soap? • Do large doses of vitamin C reduce the likelihood of getting a cold?

4. Science • Not simply a body of knowledge or a list of facts to be remembered… • …but rather an intellectual activity, encompassing observation, description, experimentation, and explanation of natural phenomena.

5. “How do you know that is true?” The single question that underlies scientific thinking

6. …the importance of questioning the truth of many “scientific” claims you see on merchandise packages or read in the newspaper or on the internet.

7. You don’t have to be at the mercy of cranks, charlatans, advertising, or slick packaging. • Learn exactly what it means to have scientific proof or evidence. • Learn what it means to think scientifically.

8. Scientific Literacy • how to think scientifically • how to use the knowledge we gain to make wise decisions • increasingly important in our lives • literacy in matters of biology is especially essential

9. Take-home message 1.1 • Through its emphasis on objective observation, description, and experimentation, science is a pathway by which we can come to discover and better understand the world around us.

10. 1.2 Biological literacy is essential in the modern world. A brief glance at any newspaper will reveal…

12. Take-home message 1.2 • Biological issues permeate all aspects of our lives. • To make wise decisions, it is essential for individuals and societies to attain biological literacy.

13. 1.3 The scientific method is a powerful approach to understanding the world. If science proves some belief of Buddhism wrong, then Buddhism will have to change —Dalai Lama, 2005

15. Understanding How the World Works • Someone wonders about why something is the way it is and then decides to try to find out the answer. • This process of examination and discovery is called the scientific method.

16. The Scientific Method • Observe a phenomenon • Propose an explanation for it • Test the proposed explanation through a series of experiments ↓ Accurate & valid, or… Revised or alternative explanations proposed

17. Scientific Thinking Is Empirical… …based on experience and observations that are rational, testable, and repeatable.

19. What should you do when something you believe in turns out to be wrong? This may be the most important feature of the scientific method: it tells us when we should change our minds.

20. 1.5 Step 1: Make observations. Look for interesting patterns or cause-and-effect relationships.

21. Does taking echinacea reduce the intensity or duration of the common cold?

22. 1.6 Step 2: Formulate a hypothesis. A proposed explanation for observed phenomena

24. To be most useful, a hypothesis must accomplish two things: It must clearly establish mutually exclusive alternative explanations for a phenomenon. It must generate testable predictions.

25. The Null Hypothesis • A negative statement that proposes that there is no relationship between two factors • These hypotheses are equally valid but are easier to disprove. • An alternative hypothesis • It is impossible to prove a hypothesis is absolutely and permanently true.

26. Null and Alternative Hypotheses • Echinacea reduces the duration and severity of the symptoms of the common cold. Or as a null hypothesis: • Echinacea has no effect on the duration or severity of the symptoms of the common cold.

27. 1.7 Step 3: Devise a testable prediction. Suggest that under certain conditions we will make certain observations.

28. Devising a Testable Prediction from a Hypothesis • Keep in mind any one of several possible explanations could be true.

29. Devising a Testable Prediction from a Hypothesis The goal is to: • Propose a situation that will give a particular outcome if your hypothesis is true… • …but that will give a different outcome if your hypothesis is not true.

30. Hypothesis: Echinacea reduces the duration and severity of the symptoms of the common cold.

31. 1.8 Step 4: Conduct a critical experiment. an experiment that makes it possible to decisively determine whether a particular hypothesis is correct

32. Hypothesis: Echinacea reduces the duration and severity of the symptoms of the common cold.

36. Take-home message 1.8 • A critical experiment is one that makes it possible to decisively determine whether a particular hypothesis is correct.

37. 1.9 Step 5: Draw conclusions, make revisions. Trial and error

38. The Role of Experiments • What is important is that we attempt to demonstrate that our initial hypothesis is not supported by the data. • If it is not, we might then adjust our hypothesis.

39. Making Revisions • Try to further refine a hypothesis. • Make new and more specific testable predictions.

40. Does echinacea help prevent the common cold? Hypothesis: Echinacea reduces the duration and severity of the symptoms of the common cold.

41. 1.10 When do hypotheses become theories? Two distinct levels of understanding that scientists use in describing our knowledge about natural phenomena

42. Hypotheses and Theories • A hypothesis is a proposed explanation for a phenomenon. • a good hypothesis leads to testable predictions.

43. Hypotheses and Theories • A theory is a hypothesis for natural phenomena that is exceptionally well-supported by the data. • a hypothesis that has withstood the test of time and is unlikely to be altered by any new evidence

44. Theories vs. Hypotheses Repeatedly tested Broader in scope

45. Take-home message 1.10 • Scientific theories do not represent speculation or guesses about the natural world.

46. Take-home message 1.10 • Theories are hypotheses that have been so strongly supported by empirical observation that the scientific community views them as very unlikely to be altered by new evidence.

47. 1.11 Controlling variables makes experiments more powerful.

48. Elements Common to Most Experiments 1. Treatment • any experimental condition applied to individuals 2. Experimental group • a group of individuals who are exposed to a particular treatment 3. Control group • a group of individuals who are treated identically to the experimental group with the one exception: they are not exposed to the treatment 4. Variables • characteristics of your experimental system that are subject to change

49. Controlling Variables • the most important feature of a good experiment • the attempt to minimize any differences between a control group and an experimental group other than the treatment itself